Photochromism of Heterocyclic Fulgides. IV. Relationship between Chemical Structure and Photochromic Performance

Tomoda, Akihiko; Kaneko, Akira; Tsuboi, Hideki; Matsushima, Ryoka

doi:10.1246/bcsj.66.330

Cited by 16 publications

(9 citation statements)

References 10 publications

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“…Green-light illumination (λ peak = 532 nm) induces a retro-electrocyclization with a quantum yield of 14.4 ± 0.8% (see SI) to regenerate the open form in which the photostationary state (PSS), or equilibrated state of isomers, consists of 75 ± 5% open E and 25 ± 5% open Z (no closed isomer, see SI). These quantum yields are similar to those reported for structurally similar furyl fulgides . The PSS of FFC in toluene under 365 nm illumination, which are the solvent and wavelength we use in all experiments with QDs below, comprises 52% C, 26% E (open), and 22% Z (open) isomer (all ±5%, see SI).…”

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confidence: 77%

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Light-Triggered Switching of Quantum Dot Photoluminescence through Excited-State Electron Transfer to Surface-Bound Photochromic Molecules

et al. 2021

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This paper describes reversible "on−off" switching of the photoluminescence (PL) intensity of CdSe quantum dots (QDs), mediated by photochromic furylfulgide carboxylate (FFC) molecules chemisorbed to the surfaces of the QDs. Repeated cycles of UV and visible illumination switch the FFC between "closed" and "open" isomers. Reversible switching of the QDs' PL intensity by >80% is enabled by different rates and yields of PL-quenching photoinduced electron transfer (PET) from the QDs to the respective isomers. This difference is consistent with cyclic voltammetry measurements and density functional calculations of the isomers' frontier orbital energies. This work demonstrates fatigue-resistant modulation of the PL of a QD-molecule complex through remote control of PET. Such control potentially enables applications, such as all-optical memory, sensing, and imaging, that benefit from a fast, tunable, and reversible response to light stimuli.

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confidence: 77%

“…Figure 2b shows the three isomers of FFC, and reported for structurally similar furyl fulgides. 40 The We synthesized CdSe QDs using a previously reported hotinjection procedure. 41 The QDs have a first excitonic absorbance peak at 585 nm, which corresponds to a diameter of 4.0 nm, and estimated conduction and valence band-edge energies as shown in Figure 3a.…”

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confidence: 99%

Light-Triggered Switching of Quantum Dot Photoluminescence through Excited-State Electron Transfer to Surface-Bound Photochromic Molecules

et al. 2021

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“…[15][16][17][18] Electronic effects, e.g., by benzo-annulation of the furyl moiety as in MeBF 15 (Fig. 1a) or its replacement by other heteroaromatic systems 3,[21][22][23] shift the absorption bands and lower the photochemical fatigue.…”

Section: Introductionmentioning

confidence: 99%

Tuning of switching properties and excited-state dynamics of fulgides by structural modifications

Siewertsen

Strübe

Mattay

et al. 2011

Phys. Chem. Chem. Phys.

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The ultrafast photo-induced dynamics of the E-isomers of four selected photochromic fulgides with distinct structural motifs have been elucidated by femtosecond broadband transient absorption spectroscopy in n-hexane as solvent. E→C and E→Z isomerisations, respectively, with time constants of ∼0.12 ± 0.02 ps and ∼0.34 ± 0.03 ps taking place in parallel were found for derivatives with a methyl substituent at the central hexatriene (HT) unit. In contrast, fulgides with increased steric constraints by an iso-propyl substituent or by intramolecular bridging displayed virtually zero E→Z isomerisation, but instead a desired accelerated and more efficient ring closure in a reaction time of only ∼50 ± 10 fs. Both photoisomerisations appear to follow excited-state pathways with distinctive conical intersections. For the ring closure, direct barrierless pathways with steep downhill gradients are likely. Furthermore, the results indicate conformer-specific reactions, with ring closure exclusively by the E(α) conformer and E→Z isomerisation predominantly by the E(β) conformer, because the E(α)→Z channel is unfavoured by the faster and kinetically more competitive E(α)→C reaction. DFT calculations of the equilibrium structures showed that the sterically demanding groups at the HT unit shift the conformer equilibria towards the E(α) conformers. At the same time, they appear to cause a favourable pre-orientation of the furyl unit that accelerates the conrotatory ring closure in the E(α)→C reaction. Benzo-annulation of the furyl unit has little effect on the observed dynamics. Overall, the results demonstrate how the excited-state dynamics and thereby the photoswitching properties of fulgides can be successfully tuned and improved by structural modifications at the chromophores.

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“…Electron-donating substituents such as methoxy, dimethylamino, and methylthio groups in the 5-position of the indole ring facilitate a remarkable shift toward visible region, whereas the 6-position results in higher molar absorptivity [94]. In addition, the increased strength of the electron-donor substituents lowers the UV and visible quantum efficiencies, but the presence of electron-withdrawing substituents shifts the absorption toward lower wavelength regions [95]. Structural features and mechanisms of photoreactions in fulgides have been examined [96,97], and the reported photochemical conversion timescales are in the nanosecond range [98].…”

Section: Fulgidesmentioning

confidence: 99%

Photochromic Responses in Polymer Matrices

Ramachandran

Urban

2011

Handbook of Stimuli‐Responsive Materials

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IntroductionMany concepts of photochromic systems have been inspired by nature. An illustrative example is the reversible shape changes of the photoreceptor molecule rhodopsin in eyes that produces a cascade of molecular rearrangements responding to light illumination [1]. Upon photoexcitation, all-trans retinal undergoes isomerization to 11-cis across the double bond, thus causing shape changes. Although this event occurs at the angstrom (Å) level, there are many molecular interconnected events and responses that are not fully understood. Similar processes have been observed in certain molecules in materials chemistry, although on a much smaller and at a less-orchestrated scale. These are known as photochromic molecules, which were discovered over 150 years ago in an organic crystal of tetracene, and later on, in inorganic and organometallic materials [2][3][4]. In spite of a long research history, a quest for new photochromic materials continues. Color changes induced by ultraviolet (UV) radiation caused by trans − − cis isomerization, ring opening-closing reactions, inter-or intramolecular charge transfer, or bimolecular cycloaddition reactions are of particular interest. To make use of their photochromic behavior in various applications, photochromic entities are often incorporated into polymer matrices.While creating individual molecules and understanding their electronic properties facilitated further advances in understanding molecular mechanisms governing photochromism, useful applications require fabrication into films, sheets, fibers, or beads. This is typically achieved by incorporating photochromic molecules into macromolecular matrices by doping or dispersing, or covalently attaching them onto a polymer backbone. Since photoisomerization of chromophores alter equilibrium conformations, the dimensions of the surrounding polymer matrix play an essential role in spatial rearrangements. The dimensional classifications of the matrix effect have been extensively examined [5], with notable applications in ophthalmic lens, optical storage media, photosensors, and biomedical devices. Furthermore, the kinetics of conformational changes of polymers with photochromic moieties depends upon their physical or chemical incorporation into the matrix [6]. As one Handbook of Stimuli-Responsive Materials. Edited by Marek W. Urban

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Photochromism of Heterocyclic Fulgides. IV. Relationship between Chemical Structure and Photochromic Performance

Cited by 16 publications

References 10 publications

Light-Triggered Switching of Quantum Dot Photoluminescence through Excited-State Electron Transfer to Surface-Bound Photochromic Molecules

Light-Triggered Switching of Quantum Dot Photoluminescence through Excited-State Electron Transfer to Surface-Bound Photochromic Molecules

Tuning of switching properties and excited-state dynamics of fulgides by structural modifications

Photochromic Responses in Polymer Matrices

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